Dr. Jeff Hersh: What causes monoarticular arthritis?

Friday

Aug 8, 2014 at 11:53 AMAug 8, 2014 at 11:53 AM

By Dr. Jeff HershMore Content Now

Q: My left knee started to swell up and hurt, and my doctor said it was some kind of arthritis and he gave me an antibiotic. What can cause this?A: Arthritis is an inflammation of one or more joints. Monoarticular arthritis (MAA) involves only one joint; polyarthritis more than one joint. Although many things can cause either MAA or polyarthritis, certain underlying conditions may be more likely in one or the other. Today I will focus on MAA.There are many possible causes of acute MAA. These are often classified into four major categories:Trauma - Trauma can cause swelling and inflammation directly from injury to one of the structures that make up the joint (bone, bursa, ligament, meniscus, etc.) or indirectly from bleeding into the joint (hemarthrosis). Hemarthrosis may occur with minor trauma or even spontaneously in people with a bleeding disorder (for example low platelets for whatever reason, or from clotting factor insufficiency such as in hemophiliacs or in people on anticoagulation medications).Infection (septic arthritis) - Many types of infection can cause MAA. Gonococcal arthritis occurs when sexually transmitted Neisseria gonorrhea subsequently spreads through the blood stream to “seed” a joint. In some patients, the symptoms in one joint may resolve only to flare up in a different joint, referred to as migratory arthritis. Gonococcal arthritis is the most common cause of infectious MAA in otherwise healthy young adults.Non-gonococcal bacterial infections that may cause MAA include staph, strep and gram negative bacteria, mycobacteria (for example tuberculosis), Lyme disease and others. In addition, certain types of fungal and viral infections may also cause MAA.Crystalline diseases - Gout, due to a buildup of uric acid crystals in a joint, is the most common of the crystalline MAA’s. Although it most often affects the joint at the base of the great toe, it can occur in essentially any joint.Pseudogout was named because its symptoms can be very similar to gout, however it is caused by the accumulation of calcium pyrophosphate crystals; it is the second most common cause of crystalline MAA, others are far less common.Systemic disorders - Systemic diseases that cause other symptoms may come to medical attention, or be complicated by, acute flare-ups of MAA. For example, sarcoid, rheumatoid and psoriatic arthritis may manifest as MAA. Other systemic disorders such as inflammatory bowel disease may cause MAA. Certain benign and even malignant cancers can cause MAA; this can be due to the cancer occurring in structures in or around the joint, or due to leukemia or other cancers infiltrating a joint.This is only a partial list; there are many other possible causes of MAA. The first step in narrowing down the most likely etiology is a history and physical exam. The history may identify risk factors such as a bleeding disorder, a history of trauma, a history suggestive of a sexually transmitted disease, gastrointestinal symptoms, etc., and the physical exam may help identify if the symptoms involve a structure around the knee (such as point bone pain), if range of motion is limited or if there is fever. Interestingly, although fever often suggests infection, many non-infectious causes, such as gout, pseudogout, rheumatoid arthritis, etc., may also cause fever.X-rays may be helpful, especially if there is a history of trauma or effusion in the joint, however, the most important diagnostic test is needle aspiration of joint fluid. If the fluid is bloody, trauma or hemarthrosis must be considered. Elevated white blood cells (WBCs) suggest inflammation and very high WBCs suggest infection; a culture of the fluid can identify an infectious agent. Crystalline disease is diagnosed by crystal visualization. Other tests such as antibody tests for Lyme disease or testing for a systemic disease may be indicated.Treatment depends on the specific diagnosis. For many causes, pain medication and conservative treatment (including rest of the joint) may be all that is needed. Infectious causes may require antibiotics, and in some cases, surgical debridement. Systemic causes may require treatment for the underlying etiology. Crystalline causes may require medications to prevent a recurrence; for example medications to lower blood uric acid levels for gout may be started after an acute flare-up.MAA is common; evaluation is needed to determine the underlying cause. This will not only inform the acute situation, but is also important to help prevent future problems.A correction to last week’s column: many patients with NMO do have brain lesions, and although the present diagnostic requirement includes “two of three criteria” with one of those being an MRI showing no brain lesions, this may change in the future. Thanks to those who wrote in!—— Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.

Never miss a story

Choose the plan that's right for you.
Digital access or digital and print delivery.